1. Field of the Invention:
This invention relates to an apparatus for and methods of controlling internal combustion engines wherein a pressure sensor for detecting the pressure in an intake manifold is used to detect the atmospheric pressure, thereby eliminating any sensor for detecting the atmospheric pressure.
2. Description of the Prior Art:
In conventional apparatus for controlling engines, there has hitherto been used an electronical control for controlling the engine operation depending upon parameters, such as engine rotational frequency, intake manifold pressure, throttle opening, atmospheric pressure, etc. For such control, it has been achieved that the intake manifold pressure, or the pressure in a suction passage downstream the throttle valve for limiting the rate of air suction to the engine is detected by a pressure sensor in the form of the absolute pressure.
In a fuel control apparatus for an engine, for example, a decision for a mode of the engine operation, i.e., whether or not the engine is in its enrich mode operation, is made dependent upon the atmospheric pressure detected by the atmospheric pressure sensor, thereby deciding the duration of a pulse corresponding to the rate of fuel injection to be supplied to the engine. In an idling control apparatus for an engine in which the atmospheric pressure is detected to control the opening and closure of a bypass passage for bypassing the throttle valve, the opening and closure of the bypass passage is also controlled in response to changes in the atmospheric pressure detected by the aforementioned atmospheric pressure sensor, when the engine is driven in its idling operation.
Thus, the conventional engine control apparatus have problems of the necessity for separate atmospheric pressure sensor in addition to the sensor for detecting the intake manifold pressure, resulting in the apparatus itself being expensive.